Structure–reactivity relations in Cu/ZrO2 catalysed glycerol dehydration to acetol in continuous flow

Abstract

The selective dehydration of glycerol to hydroxyacetone (acetol) was studied in a continuous flow fixed-bed reactor with CuO supported on monoclinic (m-) or tetragonal (t-) ZrO₂ nanoparticles. Catalysts were characterised by ICP, N₂ physisorption, powder XRD, HR-TEM and SEM-EDS, N₂O titration, and NH₃- and CO₂-TPD. Quasi-in situ XPS reveals the impact of zirconia phase on copper speciation, with m-ZrO₂ preferentially stabilising Cu(I) species, whose presence correlates with enhanced catalytic performance. In situ FTIR of 1,2-propanediol and glycerol evidenced Cu(I) promote desorption of a CO containing intermediate. Solvent selection strongly influenced catalyst reactivity, with methanol less prone to competitive adsorption than water, and favouring the genesis of Cu(I) species. Cu/m-ZrO₂ achieved 60% yield of the desired acetol at 240 °C, maintaining ≥50% yield over three consecutive regeneration cycles, being one of the most efficient catalysts based on earth abundant metals for continuous glycerol dehydration to acetol under the present conditions.